This invention relates to means for reducing the power which is required to drive the movable parts of an industrial robot or the like, and more particularly to a balancing device for balancing the force of action between the driven part and the driving part.
For instance, in an industrial robot using cylindrical coordinates, the means for lifting the robot hand is made up of a vertical feed screw and an electric motor for driving the feed screw. In this case, the weight of the robot hand, the light weight of the movable frame which supports the robot hand, the weight of an object gripped by the robot hand, and external forces produced during acceleration of deceleration are exerted on the feed screw. Accordingly, the capacity of the drive motor should be large enough to deal with the combination of the above-described forces. Therefore, although only a small amount of power is required to lift the object, the motor capacity must be large. This represents a loss in the drive system.
In order to avoid this drawback, in the prior art, the rod of an air cylinder is used to provide an upwardly directed force on the movable frame, so that the light weight of the movable frame, etc. are cancelled by the upwardly directed force, whereby the motor load is reduced. However, such an air cylinder must be considerably long. If such an air cylinder is employed, the resultant device is unavoidably large in size. Therefore, the application of such a device to an industrial robot is rather difficult.